It was the first faction to form and the first state to secede when the Governor of California declared home rule in his state and California seceded from the United States of America on April 15, 2013. Texas followed quickly, declaring sovereignty and re-forming the Republic of Texas. Both California and Texas took neighboring states with them and share a national border with each other at the start of the game. The California Commonwealth is at least partially responsible for the formation of the northwest alliance of former states called Pacifica, since Pacifica formed after refugees from San Francisco were evicted from their homes by Californian militia.

In-game description:

"The California Commonwealth is made up primarily of the former states of California, Nevada, Arizona and Utah. Although the faction is wealthy in natural resources, most of the population centers are on the Pacific coast. Typically, others see members of the California Commonwealth as shallow but with an eye for color. The reality is they are also creative and resourceful. Most members of the California Commonwealth see the war as a battle against restriction and oppression."

FCS Jackson tanks attack Pacifican forces up close and personal outside San Francisco.

The California Commonwealth starts with and is able to manufacture an array of former U.S. military units. California Commonwealth units appear on-map with an orange or coppery coloring to them, and include:

The California Commonwealth designed a unique heavy tank called the FCS Jackson, named after famed Confederate war hero Thomas J. "Stonewall" Jackson. The FCS Jackson is not truly a main battle tank, however, as it features only flamethrowers and missile launchers. This makes it devastating against infantry and light armored targets, but due to its limited firing range and lack of any actual main gun it fights other heavy armor at a disadvantage. The FCS Jackson is the only unit in the game to use flame weapons, featuring a pair of flamethrowers on the front of its hull.